When to pull power back on takeoff.

[svcta]

Numerous noise abatement proceedures in aircraft regard a quick climb, power reduction leveling of attitude until past noise sensors or a noise abatement area, then a return to a climb power setting. In propeller driven aircraft, this is often best accomplished by a RPM reduction, which may or may not be accompanied with a power reduction. In some aircraft, reduction of RPM just after takeoff may be accomplished for operational needs, noise abatement, or merely because it's the best power setting.

SOP in our 4Y's, for example, was breakaway thrust to become airborne, then a power and RPM reduction...the reduction was far more likely to enhance safety than any issues with the mythical but nonexistant engine-failure-with-the-first-power-reduction monster, because we were more interested in avoiding lifting a cylinder head than avoiding something that does not exist.

I do a lot of flying that doesn't climb very high...I may never climb more than a few hundred feet for the entire duration of the mission, and yes, reduction of power after takeoff, or reduction of RPM, is quite appropriate. Not uncommonly I'll back off the high RPM stops either during the takeoff roll, or just after breaking ground, while levelng at 5' to retract flaps, before climbing to 15-25' make the crosswind turn. Strange thing is, the airplane doesn't melt down, explode, or fall out of the sky because of this heretic maneuver. It may be outside the small, diminuitive box in which you operate, but it is appropriate to the mission.

Yes, mission. You fly profiles, I fly profiles. When appropriate. I am assigned sorties and missions, and they're logged accordingly. I'm paid accordingly. Perhaps you have trips, or dispatches, or rigs, or whatever you want to call them. But in every case, we each have a mission to perform, be it point to point, or some form of working operation such as utility flying. The purpose of the flight is the mission, the assignment, the duty, the plan, or whatever you desire to call it. We simply call it the mission, ice dude.

No, an 0-470, 0-520, or 0-550 isn't a big engine. A R-1340 isn't a big engine, so far as pistons go. A R-3350 or R-4360 is a big engine. Light aircooled horizontally opposed recip piston engines are small engines. As you will. Calling the engines found in a Cessna 340 or 400 series cessna "big" is worth a chuckle, though.



How would you phrase that if you weren't a college graduate?

Not that you have a need to know, but I don't rent. I don't fly a dutchess, and my butt is just fine, thanks. However, if I reduce power in said airplane, your diminuitive comfort zone would have the world believing the aircraft will come raining down from the sky...when such is a ridiculous notion. Highly melodramatic, but stupid. Never the less, you're just too disinterested to care.

Folks like yourself are the reason that places like Santa Monica are so tough on noise and are rapidly becoming restricted to the rest of us. Such shortsightedness in thinking only of yourself hurts everyone. You're responsible for the damage being done to the industry, animosity toward operations at many noise sensitive airports, and limitations that we continually face as airports are closed, arrivals and departures limited, and penalties and curfews increasingly placed by communities all over. Thanks for your help!

My friend, try reading a little.

1. yes, a noise abatement climb is a max effort climb followed by a level off and subsequent power reduction. You've now agreed with me.

2. Your engine will not fail with a power reduction(in all likelihood, mileage may vary, these are just statistics). You've now agreed with me.

3. You've obviously got a lot of mission-specific operational guidelines to follow that extend beyond what many would consider to be normal, I'm totally okay with that, but these considerations were never a part of the original conversation. My whole point has been with dealing with marginally powered light aircraft or jets. I've admitted to the same "heretic" maneuvers regarding early power reductions in aircraft that have the balls to back it up. In a sense, you've agreed with me.

4. I've never used the word "dude" on this board(caveat:that I can recall). You've got the wrong dude, dude.

5. An IO-550 is, in fact, a big Continental(and they need to be operated more carefully than Lycomings, in my opinion, so the name does matter). That cannot be argued. I never said "big reciprocating engines". By shear number of piston powerplants in the world, however, an R-1340 is still pretty big. I agree there are much bigger ones out there, but it's bigger than most and therefore relatively large. Don't know what else to say about that.

6. I never graduated from college, what's your point?

7. Okay, I'll admit: If I were in an underpowered airplane I wouldn't enjoy limiting my already limited climb performance. This makes me a bad pilot how? I NEVER said that it would cause airplanes to "rain from the sky", but it doesn't make sense to put yourself in that position does it? Once again, different in airplanes with a little guts.

8. Don't you dare give me this "folks like you" crap. I haven't flown out of anything other than private airports in recips (except for airshows) in years, and I've explained how I handle that. And I've also already told you that in a jet I play ball like I need to(even with the stage 3 noise signature). I've never been fined or been called out for busting a noise abatement procedure.

9. I said that rented Duchesses are busted-a$$, not you. Why so sensitive about it?

 

[avbug]

No need to apologize. Have yourself a merry little christmas.

 

[Rally]

The only complete failure was about 30 secs after a power change at 700 agl. Although talking to people that have had engine failures (not fuel or related) have been probably about 50/50. It is probably a myth, as is oversquared as is pull the power back at 1000 agl or 500 or when the wheels are up. I think it depends on the a/c. I think the most important thing was in the original question. The aircraft is a Mooney 20C manual says at a comofortable altitude pull power back to I think 2650. No manifold reduction. Another manual of a Stinson 108 says pull back to 23 inches as soon as it is resonable, for "noise". Not sure what they mean by noise but to me the prop makes the most noise. This was a test bed aircraft redesigned by Univar. The stinson has a Lycoming IO360 same as a Arrow. To me I'll take as reasonable to mean 1000 feet. 500 feet does'nt make a difference. IFR in fog I don't touch *hit till I break out or at least 1000 agl, why mess around? Cessna 172 manual for a OLD OLD 172 says to pull back the manifold (not CS prop on this a/c) to comfortable setting that allows a good climb to save the engine. I guess in all cases, follow the FAA/POH recommendations?
I don't believe in making up my own procedures for a a/c I did'nt design or regulate.

Thanks

 

[unreal]

At full throttle the "power enrichment valve" is opened making your mixture supper rich to aid cooling. Back it off to 25" and that valve closes creating hotter temps. Nowere in a Cessna 182 POH does it sugest partial power climbs. I leave it wide open to altitude.

I'd never heard of the power enrichment valve until I read this topic. The avweb article another poster linked alluded to the idea that this type of thing was typically on bigger flat 6s and radials. Do engines such as the O-360 on a Seminole have power enrichment valves as well? My school is very adamant about the whole 25"/2500 RPM rule at 500', and I've often wondered the real reason behind it other than "that's how we do it." I'll check the POH when I have one handy, but I don't seem to recall seeing that procedure in it.

 

[avbug]

The enrichment valve, or economizer valve, is part of the carburetor, not the engine. Some installations use this feature, others do not.

The enrichment cools the engine and helps prevent deonation at higher power settings. You can lean off the economizer, but if you do, you can't set your mixture for takeoff based on your runup at say, 1,700 RPM. A partial power runup is no good to set the mixture before departure, because your mixture will change drastically at full throttle. You need to run up to full throttle and set your mixture there, which is why I generally recommend setting the mixture on the runway and not before.

When you retard power, you'll need to enrichen the mixture, because as soon as you reduce power and come off the enrichment flats, you're leaning the engine automatically...you need to enrichen it using the mixture before you retard the power.

As far as reducing power...there are proceedures, and then there is technique. Using pilot technique doesn't negate or remove procedure. One may have many different techniques for operating an airplane, and still be acting in accordance with manufacturer recommendations and proceedures. A power reduction after takeoff is one such technique.

Many pilots are highly ignorant of their aircraft and it's operation, and often do things because that's the way they were taught...probably would walk if a cliff if they were taught to do it, too.

If you're running on the enrichment valve and are aggressvely leaned, then retarding power may cause an engine failure from either fuel starvtion or detonation. Again, this isn't the fault of reducing power, but the pilot who doesn't increase the mixture first...which is typically caused by being ignorant of the presence of this feature in the aircraft to begin with. Many pilots are quite happy to never go beyond reading the POH or AFM...and miss important information such as this which may or may not be in there. Ask around and see how many others who are flying aircraft such as a carbureted 172 are aware of the economizer valve, it's function, and it's requirements and pitfalls. Not very many, but they're more than happy to keep on instructing in the aircraft when they don't understand the system. Go figure.

 

[USMCmech]

I'd never heard of the power enrichment valve until I read this topic. The avweb article another poster linked alluded to the idea that this type of thing was typically on bigger flat 6s and radials. Do engines such as the O-360 on a Seminole have power enrichment valves as well? My school is very adamant about the whole 25"/2500 RPM rule at 500', and I've often wondered the real reason behind it other than "that's how we do it." I'll check the POH when I have one handy, but I don't seem to recall seeing that procedure in it.

Yes, the carb on the lycoming O-360 uses an enrichment valve.

Watch the fuel flow when you back off the throttle. By moving the throttle back slightly you will see a LARGE drop in fuel flow, that is the result of the valve closeing.

I too was taught to pull the power back to 25" after the initial climb. However it is actually harder on the engine than leaving it at full throttle.

 

[avbug]

Not all O-360's use the enrichment valve...some engine installations do, some don't. Again, it's a functin of the carburetor that's assigned to the engine installation.

Reducing back to 25" isn't harder on the engine, though it may reduce performance slightly.

 

[FrozenPilot]

Company profile, POH, personal preference, in that order.

Not that I've seen anything definitive for the IO-540s in the Aztec, so I usually leave everything forward til I feel comfortable, may be 200AGL, 1000, or something else. First adjustment I make is pulling the props back to 2400, then MP to 25", then lean slightly to 17-18gph. Thats not what they teach at flight school. Deakin's articles are pretty enlightening. Though this way oversimplifies things, as long as you avoid detonation and keep within the redlines, you can do pretty much anything.